1. Field of the Invention
The invention relates to a method and an apparatus for decorating containers.
2. Description of the Related Art
Containers of this type may be made of paper, plastic, glass or metal, and are mainly used in the beverage, food and cosmetic industry. Such containers are decorated by using transfer processes and corresponding devices.
Typically, containers have a cylindrical shape. Various methods and devices for decorating cylindrical containers are known. An exemplary method and an apparatus for a thermal transfer process is disclosed in DE 195 09 984 C1 (corresponding to U.S. Pat. No. 6,098,689). Herein, the containers move on a transport path while rotating, and decors move past a transfer location on a carrier conveyor, where the decors are transferred to the containers through application of pressure and heat. The transport path and the carrier conveyor move in opposite directions. The circumferential velocity of the containers corresponds to the velocity of the carrier conveyor, while the necessary transfer heat is produced by heating the carrier conveyor.
Unlike other known processes, the containers used with this process have a particularly high circumferential velocity which is determined by the opposing moving directions of the carrier conveyor and the transport path. This provides a continuous transfer at a high velocity and with excellent quality, because the spacing of the containers on the transport path and the spacing of the decors on the carrier conveyor can be independent of each other. In addition, the corresponding apparatus is much simpler because different movements do not have to be matched with each other.
However, the method and the apparatus disclosed in the reference are not suitable for decorating containers having a non-cylindrical shape. However, the industry uses more and more frequently containers, in particular PET bottles, having a particular shape in order to give the product a distinguishing characteristics. Until now, such containers could only be labeled or printed using discontinuously operating machines, which is an inefficient process that has been rejected by the industry in applications where large production quantities are required.
It is therefore an object to develop a process and an apparatus for continuously decorating cylindrical as well as non-cylindrical containers.
This object is solved by a method for decorating containers, wherein the containers (1) are moved on a transport path (5) and the decors are moved with a constant velocity on a carrier conveyor (10) in the opposite direction and tangentially at a transfer location (11), where the decors are transferred sequentially to the containers (1) by applying pressure and heat, and are subsequently subjected to a thermal treatment, wherein the ratio of the spacing of the containers (1) to the velocity of the transport path (5) is the same as of the ratio of the spacing of the decors to the velocity of the carrier conveyor (10) and wherein the containers (1) are accelerated in the region of the transfer location (11) to a circumferential velocity which corresponds to the velocity of the carrier conveyor (10), characterized in that
before the transport location (11), the containers (1) are decollated to have a uniform spacing and are rotated and then stopped and secured in a predefined position based on a marking (30) on the container (1),
the secured containers (1) are accelerated at the transfer location (11) to the required circumferential velocity, and
a contact line between the carrier conveyor (10) and the rotating container (1) is established by a freely rotating transfer roll (26, 31) of a pressure head (6, 6xe2x80x2) which moves with and is returned with the transport travel of the container (1) and can also be moved transversely to the transport path (5), wherein the contact line is maintained over a predetermined path of travel of the container (1) and by a device for decorating containers, comprising a transport path (5) for containers (1) having a uniform spacing and a carrier conveyor (10) for decorations having a uniform spacing, with the transport path (5) and the carrier conveyor (10) contacting each other with opposite rotation directions at a transfer location (11), wherein a pressure head (6) for applying a pressure to the transport path (10) towards the container (1) is arranged at the transfer location (11) and the transport path (5) includes a thermal post-treatment device (7) located after the transfer location (11) and the carrier conveyor (10) includes a heating device located before the transfer location (11), characterized in that
the transport path (5) comprises a rotatable receiving device (22), which secures the position, and a positioning device (13), wherein the positioning device (13) is provided with a rotary drive and a position detent (16) which matches a marking (30) on the container (1) and interrupts the rotation of the container (1), and
each receiving device (22) is designed so it can be driven together with the container (1) at the transfer location (11) in the direction on the carrier conveyor (10), and the pressure head (6) is provided with a pressure-biased movable transfer roller (26, 31), wherein
the transfer roller (26, 31) is constructed so as to be able to rotate and travel with the container (1), and to move transversely to the transport travel of the containers (1).
Various preferred features of the present method are as follows:
the rotation for orienting and securing the container (1) is provided by a separate drive and is stopped at a predetermined position;
a cylindrical portion of the freely rotating container (1) rolls on a stationary friction element (15) over a predetermined rotation angle;
the containers (1) are oriented and secured on a feed star arranged before the carousel (4) and that the secured containers (1) are conveyed to the rotatable receiving devices (22) of the carousel (4), where the secured containers (1) are again secured in their respective position;
the containers (1) are secured on the carousel (4) by a friction force and each receiving device (22) is driven by the carrier conveyor (10) against the friction force in the region of the transfer location (11);
the receiving devices (22) are supported by a separate drive unit and that each receiving device (22) is rotated by this drive unit in the region of the transfer location (11);
the transfer roller (26, 31) is returned to its initial position by a linear motion after a label has been applied to a container (1);
the transfer roller (26, 31), after application of a label to a container (1), is returned to its initial position by a rotating motion about a pivot located outside the carousel 4;
to compensate for the different circumferential velocity of the container (1), the rotation of the container (1) or the transport motion of the carrier conveyor (10) has a non-uniform velocity which matches the circumferential contour of the container; and
to compensate for a different circumferential velocity of the container (1), the decors on the carrier conveyor (10) have a distortion which is matched to the circumferential contour of the container (1).
Various preferred features of the device according to the invention are as follows:
a drivable feed star (2) is located before the carousel (4), wherein the positioning device (13) is arranged on the feed star (2) and the receiving device (22) is arranged on the carousel (4), and that both are functionally connected at a transfer location;
the rotational drive of the positioning device (13) comprises a receiving pocket (14) in the star (12) of the feed star (2) and a stationary friction element (15), both being dimensioned and arranged so as to match a cylindrical portion of the container (1);
the positioning device (13) comprises a position detent (60) which is rotatably supported in the star (12) of the feed star (2), with the position detent (16) having a drivable roller (18) and a positioning finger (20) which matches the marking (30) of the container (1) and a spring arrangement (21) acting towards the center of the container (1);
the receiving device (22) comprises a rotatable and drivable receiving plate (23) having a surface which matches the bottom contour of the container (1) and a centering head (24) which acts on the opening of the container (1);
the centering head (24) of the receiving device (22) includes a supply channel (25) for blast air which produces a counter-pressure in the container (1);
the carrier conveyor (10) for the decor is designed to form a drive for the receiving device (22);
the pressure head (6) is designed so that it can rotate and be driven in the direction of the transport travel of the container (1) and has at least three transfer rollers (26) which are each supported above a piston cylinder unit (28) at a pivot point located outside the carousel (4) and connected to each other via articulated arms (27), wherein the spacing between the transfer rollers (26) corresponds to the spacing between the containers (1) on the transport path (5);
four transfer rollers (26) are combined to form a movable parallelogram;
the transfer roller (26) which contributes to the transfer, is biased by a stationary cam having a shape which complements the contour of the container;
the articulated arms (27) are in the form of heating plates for the carrier conveyor (10);
the pressure head (6xe2x80x2) can rotate and be driven in the direction of the transport motion of the container (1) and that the transfer rollers (31) are arranged on a circular track of the pressure head (6) and are operatively connected with a pressing unit (33), wherein the pressing unit (33) can be pivoted about a pivot point (34) located outside the rotation axis of the pressure head (6xe2x80x2) and is supported for radial displacement relative to a rail (35) which can be pivoted about this pivot point (34), and the pivoting and displacement motion have separate drives in the contact region with the container (1);
the pressing unit (33) is driven by a cam gear to provide the pivot motion and the displacement motion for adjusting the circular path of the transfer roller (31) and that the pressing unit (33) is driven by a pressure medium in order for the displacement motion to adapt to the surface contour of the container (1);
the pressing unit (33) is a piston-cylinder unit;
with each transfer roller (31) there is associated a pressing unit (33) which rotates together with the pressure head (6xe2x80x2);
a stationary pressing unit (33) is associated with all transfer rollers (31), wherein the stationary pressing unit (33) is constructed to be drivable in the contact region by the rotating motion of the rotating pressure head (6xe2x80x2) so as to move together with the transport motion of the container (1), and the stationary pressing unit (33) has a separate drive for the return travel; and
the transfer rollers (16) are spaced apart on the annular path of the pressure head (6xe2x80x2) by retaining elements (32) which are also formed as a guide element and optionally as a heating element for the carrier conveyor (10).
This solution eliminates the disadvantages of conventional methods and devices.
It is particular advantageous that cylindrical as well as non-cylindrical containers can be decorated by a continuous process, without foregoing the advantages of the conventional methods for decorating of cylindrical containers.
A particularly important feature is the pressure head which is disclosed in two different embodiments. It is particularly advantageous with non-cylindrical containers if the pressure head, which has rotating rollers and a pressing unit, is implemented in the form of a piston-cylinder unit. In this way, uniform force components are produced at the transfer location, thereby preventing a distortion of the decor.
To reduce costs and complexity, the support elements arranged between the transfer rollers also operate as a guide path for the support conveyor and as heating elements.
Embodiments of a method and a corresponding apparatus of the invention will now be described.